/*
 * Copyright 2014 Netflix, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.netflix.servo;

import com.netflix.servo.monitor.Monitor;
import com.netflix.servo.util.Preconditions;
import com.netflix.servo.util.UnmodifiableList;

import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

/**
 * Simple monitor registry backed by a {@link java.util.Set}.
 */
public final class BasicMonitorRegistry implements MonitorRegistry {

  private final Set<Monitor<?>> monitors;

  /**
   * Creates a new instance.
   */
  public BasicMonitorRegistry() {
    monitors = Collections.synchronizedSet(new HashSet<>());
  }

  /**
   * The set of registered Monitor objects.
   */
  @Override
  public Collection<Monitor<?>> getRegisteredMonitors() {
    return UnmodifiableList.copyOf(monitors);
  }

  /**
   * Register a new monitor in the registry.
   */
  @Override
  public void register(Monitor<?> monitor) {
    Preconditions.checkNotNull(monitor, "monitor");
    try {
      monitors.add(monitor);
    } catch (Exception e) {
      throw new IllegalArgumentException("invalid object", e);
    }
  }

  /**
   * Unregister a Monitor from the registry.
   */
  @Override
  public void unregister(Monitor<?> monitor) {
    Preconditions.checkNotNull(monitor, "monitor");
    try {
      monitors.remove(monitor);
    } catch (Exception e) {
      throw new IllegalArgumentException("invalid object", e);
    }
  }

  @Override
  public boolean isRegistered(Monitor<?> monitor) {
    return monitors.contains(monitor);
  }
}
